Field weakening capability investigation of an axial flux permanent-magnet synchronous machine with radially sliding permanent magnets used for electric vehicles

Due to the advantage of high power density compared with the conventional radial flux machines, the axial flux permanent-magnet synchronous machines (PMSMs) are very suitable candidates for the power train of electric vehicles (EVs). In this paper, a new axial flux PMSM adopting radially sliding permanent magnets (PMs) to fulfill field-weakening control and to improve the operating speed range is investigated. The field-weakening structure and principle of the axial flux PMSM with radially sliding PMs are proposed and analyzed. The influence of radially sliding PMs on electromagnetic performances and parameters is analyzed based on FEM. The field-weakening method with radially sliding PMs, which is a mechanical method, is compared and combined with traditional electrical method. Due to the optimized combination of the two methods, the field-weakening capability of the machine is much improved and the maximum speed can reach up to six times of the base speed with constant power, which is very satisfying for EV drive application.